Hydroplane surfboard



Dec. 15, 1964 KELLY, JR 3,160,897

HYDROPLANE SURFBOARD Filed April 15, 1963 2 Sheets-Sheet l INVENTOR.JOHN M. Kim; J/Q

M wiw 1366- 1964 J. M. KELLY, JR

HYDROPLANE SURFBOARD 2 Sheets-Sheet 2 Filed April 15, 1963 JOHN M. AFLD,we

A 7'70/P/V5KSY United States Patent" 3,169,397 HYDRGPLANE SURFEGARD JohnM. Kelly, In, 4117 Black Point Road, Honolulu, Hawaii Filed Apr. 15,1953, Ser. No. 273,924 4 Claims. (Cl. 9-310) This invention relates to asurfboard.

Most surfboards now in use are made with curved 1ongitudinal profileswhich rock about their centers of gravity in a manner to aid the riderin maintaining his fore-andaft balance and to allow the board toapproximate the curvature of the forward slope of the wave. The majordisadvantage in such a rocker construction is that the board drags aquantity of water when moving directionally over and through the waterthereby inhibiting its speed which limitation cannot be overcome by therider. While drag may be desirable when the rider wishes to stall andthus ascend to a higher position on the wave, he

also needs maximum speed capability to shoot the curl,

i.e. to plane across the face of the wave, perhaps the most desirableriding maneuver. may need to stall again or to turn at high speed toavoid hitting another rider, to avoid rocks or to navigate wind chops orunevenness on the waves slope.

Other surfboards now designed for use exclusively in big surf, i.e., forwaves above feet in height, are constructed to maximize speed byminimizing the rocker curvature and providing sharp breakaway edgesaround the stern. However, because of their elongated, straight andrelatively flat tails which are adverse to the curved path of thesurfboard when engaged in turning, these boards are inherently incapableof maneuvering at high or at low speeds. Thus, these boardssacrificemaneuverability to achieve high speeds whereas the aforementioned rockerboards sacrifice speed for maneuverability.

The primary object of .the invention is to overcome the aforementioneddisadvantages resident in the conventional surfboards by combining in asingle surfboard acces- ,sibility of both extremely high as well as lowspeeds and increased maneuverability at all speeds- This combination ofheightened functions is accomplished by providing a planing surface anda scorpion tail which are physically differentiated by a transverseshoulder so that the rider, by body movement or shift in weight, canbring the planing surface into partial or full play or bring the draginto effect thereby achieving a wide range of speeds while maintainingmaneuverability throughout.

Another object of the invention is to provide a surfboard which readilyenables the rider to attain a wide range of ,speeds as well asaccentuated maneuverability at all speeds by the functional coactionbetween a number of features which comprise a planing surface and ascorpion tail which are differentiated physically by a transverseshoulder thereby creating discretely separated bottom surfaces,

At any moment, the rider the tail curving upwardly above the wake andtapering.

towards its tip away from the shoulder to provide a cutaway at the sidesof the board in the location of the tail. The cutaway, taking advantageof the clean partition of the water from the board at the sharpbreakaway edge of the transverse indentation at the bottom and sides,acts 'as a means to prevent the water from being sucked in U around thestern and create a drag from which the rider i cannot release himself.The same is true for the lift of the tail. I V v Another object of theinvention is to provide a surfboard which enables the rider to attain awide range of speeds, a. greater maximum speed, and accentuatedmaneuverability, yet the board'is relatively simple in designconstruction and easier to operate than other models.

These and other objects and features of the lnvention 1 will become moreapparent as the following description proceeds in conjunction with theaccompanying drawings, wherein:

PEG. 1 is a side elevational view of the surfboard;

FIG. 2 is a bottom plan View thereof;

FIGS. 3, 4 and 5 are fragmentary elevational views of modified forms ofshoulders;

FIG. 6 is a fragmentary bottomplan view of modified forms of a board atthe aft end of the planing surface and scorpion tail;

FIGS. 7, 8 and 9 are fragmentary enlarged views of the tail end of thesurfboard illustrating respectively low, partial and maximum drag;

FIG. 10 is a fragmentary vertical sectional view through the board justaft of and looking at the shoulder and illustrating one type of sideedge at the planing surface; and

FIG. 11 is a view similar to FIG. 10 illustrating another type of sideedge at the planing surface.

Specific reference is now made to the drawings wherein similar referencecharacters are used for corresponding elments throughout.

The surfboard of the instant'invention is generally indicated at 10 andis an elongated member capable of being fabricated of a wide variety ofmaterials, preferably fiberglass-covered air-expanded plastic foam orbalsam wood. The rider engages the upper or deck face 12 while theopposite or bottom face 14 is adapted to engage the water. The how 16 istapered and preferably upwardly curved to provide a scoop, whereas thestern includes an upwardly curved scorpion tail 18 having a bottom ortail surface 22.

The bottom face 14 includes two separate and distinct surfaces, one thetail surface 22 and the other a planing .surface 24 forward thereofhaving a skeg 24 depending from its after end. 7 These surfaces aredifferentiated by providing a transverse shoulder 26 formed in thebottom face which consists of a break in the lines of the side andbottom profiles in such a manner that the tail surface 22 is elevatedabove the planingsurface 24. The maximum depth of the shoulder, i.e.-thedistance bywhich the tail surface 22 and the planing surface 24 areseparated, may vary from one-eighth to'four inches depending .upon thebody weight and preferences of the riders as to height of the waves tobe ridden, the degree of slope of the waves at which the higher speedsare desired and the degree of braking effect desired, the depth ofmaximum efficiency proceeds aft curving inwardly from both sides to meetat a point varying from approximately two inches from the stern to apoint midway between the bow andstern depending upon the overall lengthof the-board and the preferences -of the rider as to maximum speeddesired,

degree of braking effect and sharpness of turning ability, the locationfor average desired capabilities being ap proximately six to eighteeninches from the stern for surfboards averaging eightto twelve feet inoverall length,

saidshoulderdeepening as it curves upwardlyin the rearward direction toits maximum depth. As. shown in solid lines in FIG. 6, an alternativeconstruction is one in which the shoulder 26 may be convexly curvedtowards .the tail as at 25 but cutoff at its apex along'a line 27transverse to the longitudinal axis ofthe surfboard. The tailmay becorrespondingly convexly tapered and facture, as well as to reducedanger of too sharp a breakaway edge, the same may be rounded to aradius of curvature of approximately one-quarter of an inch. It shouldbelunderstood, however, that a sharper breakaway edge is functionallypreferable due to hydrodynamic action of fluids in separating from planesurfaces. The shape of the shoulder as viewed from .the. side may varyfrom a deep recess or acute angle 39 as shown in FIGURES 1, 2, 3 and 7-9through a substantially right angular recess 32 as shown in FIGURE to ashallow recess 34 somewhat iii-excess of ninety degrees as shown inFIGURE 4. V Z a The planing surface 24 functions at maximum efliciencywhen it is fiat, both transversely and longitudinally, al-

though it may be curvedboth longitudinally and trans-,

Versely, the degree of longitudinal curvature being least at theshoulder and greatest where the planing surface and bow scoop merge asat 36, see FIG. 1. The side edges of the planing surface may be roundedas, shown at in FIG. 11 'to causethe board to groove slightly into thewave but for maximum etiiciency they fair down gently from the deck atan angle of approximately fortyfive degrees to end in sharp sidebreakaway edges as shown at 42in FIG. 10; The radius of curvature ofeach side edge from the shoulder forward a distance approximately equalto the length of the planing sur-. face, for maximum efiiciency, shouldnot exceed onethirty-secondth of an inch, the edge becoming rounded Iii.

greater speed. In either case of indentation or absence thereof, thescorpion tail should lie within and not ex- .ceed the dimension acrossthe wake area as produced by the shoulder, the planing surface and themaximum .Wldth of the surfboard forward of the shoulder.

The edges of the scorpion tail are so curved that tail surface 22 fairsgradually upward to meet the deck surface 12 in a high-drag breakawayedge comprising the periphery of tail 18 the radius of curvature beingnot iess than one-eighth of an inch at the edge itself but with maximumdrag effect being achieved with a curvature of approximately one andone-half to two inches radius.

The skeg 2%) should be long enough to extend from approximately two totwelve inches below the line extending aft of chaplaning surface 24 withmaximum efiiciency being achievable for turning at all speeds when theskeg is located at the aft end of the planing surface.

In use, the rider stands on the deck of the board and by leaning hisweight on the forward foot he brings the planing surface 24 into partialplay and by taking a stance farther forward brings it into full play. Byleaning back on the foot placed to the rear, he minimizes planing andbrings the drag into effect. FIG. 7 shows the condition of thewater '44at low drag yielding high speed, FIG. 8 shows the condition at partialdrag yielding intermediate speed and FIG. 9 shows the a condition atmaximum drag yielding slow speed. The

as it merges with the rounded sides of the board at the a bow end. r v

The dimensions of the planing'surface 24 may vary according to theoverall dimensions of the board and height, weight, and individualpreferences of: the rider,

said planing surface comprising that-longitudinallyv fiat area situatedbetween thejuncture 28 of shoulder 26 with planing surface 24 and thearea of the commencement of the bow scoop' 36, but in the event of thecurvature of the scoop extendingaft to' the juncture 28, the

planing surface constitutes the wetted portion of the undersurface inriding .position, excluding the scorpion tail, which varies in length,width and area as to the weight of the rider and trim and speed inriding posi-' tion on the wave. The instant board can have a straightinstead of an uplifted bow, in which case the planing surface extendsfrom the shoulder forward to the bow extremity of the board therebycomprisinga major portion of the total bottom surface.

The entire section aft of the shoulder 26 is the scorpion tail 18 whichis elevated above the planing surface in the manner indicatedhereinbefore with reference to the depth of the shoulder. The: scorpiontail is curved both longitudinally and transversely and upwardly fromthe.

plane of the planing surface, the upward curvature varying from slightlyabovethe plane to a maximum of approximately eight inches measured fromthe tip-10f the tail to the extension of the; plane aft of the shoulder.

It will be seen from'FIG. 2 that the sides of the scorpion tail curveinwardly or taper in diminishing width from the shoulder to the tip: ofthe tail to provide a cutaway 38, which is the space between theextensions 5' aft of the sides of the board beyond the'shoulder and thesides of the tail as seen in FIG. 2. .The sides of the scorpion tail atthe shoulder may be sharplyindented scorpion tail provides a. curvatureadapted to the shape of the turning circle when depressed into the waterthus enabling the rider to attain superior turning capability. Thecutaway 33 at the tail enables the water to part cleanly from the sidesof the board rather than be sucked in around the stem at all times, ason conventional boards, thereby creating drag from which the ridercannot release himself. Thus, with the instant surfboard, therider'can-achieve any degree of speed while maintaining maneuverabilitythroughout.

This application is a continuation-in-part of my copending applicationSerial No. 226,045 filed September 25, 1962, now Patent No. 3,111,695.

I claim: 7

l. A surfboard comprising an elongated member having a deck and a bottomface, and a vertically and transversely extending shoulder in the bottomface dividing said face into two discreet vertically spaced surfaces,the

of said shoulder, and a skeg depending from the after end of saidplaning surface the normal stance of the rider for planing being withone foot over the skeg and the other foot forwardly thereof over theplaning surface.

2 A surfboard comprising an elongated member having a deck and a bottomface, "and a'vertically and transverselyextending shoulder in the bottomface, dividing said face into two discreet vertically spaced surfaces,the

upperone extendingaft of the shoulder to the stern and constituting atail surface and the lowerone extending L forwardly of the shoulder andconstituting a planingsurface, theportion of theboard aft of saidshoulder being a scorpionstail whose sides taper inwardly towards thestern to provide a cutaway-portion between the sides of the tail andextensions of theaside s of the board aft of said shoulder, said.shoulder being convexly curved toward the tail. 1 r

' 3. A' surfboard comprising an elongated member having a deck and abottom face, and a vertically and transby acute angles or by rightangles or may also be continuous with the curvature of the sides oftheboard, though the aforementioned indentation affords less dragandf/er'sely extending shoulder 'il'lfi'hfi bottom face dividing said faceinto two discreet vertically spaced surfaces, the upper one extendingaft of the shoulderto the. stern and constituting a tail surface and thelower one extending forwardly of the shoulder and constituting a planingsurface, the portion of the board aft of said shoulder being a scorpiontail whose sides taper inwardly towards the stern to provide a cutawayportion between the sides of the tail and extensions of the sides of theboard aft of said shoulder, said planing surface being transverselycurved, said shoulder being convexly curved toward the tail and a skegdepending from the after end of said planing surface.

4. A surfboard comprising an elongated member having a deck and a bottomface, and a vertically and transversely extending shoulder in the bottomface dividing said face into two discreet vertically spaced surfaces,the upper one extending aft of the shoulder to the stern andconstituting a tail surface and the lower one extending forwardly of theshoulder and constituting a planing surface, the portion of the boardaft of said shoulder being a scorpion tail whose sides taper inwardlytowards the stern to provide a cutaway portion between the sides of thetail and extensions of the sides of the board aft of said shoulder, saidshoulder being convexly curved toward the tail, and a skeg dependingfrom the after end of said planing surface.

Eicholtz Feb. 14, 1961 Kelly Nov. 26, 1963

1. A SURFBOARD COMPRISING AN ELONGATED MEMBER HAVING A DECK A BOTTOMFACE, AND A VERTICALLY AND TRANSVERSELY EXTENDING SHOULDER IN THE BOTTOMFACE DIVIDING SAID FACE INTO TWO DISCREET VERTICALLY SPACED SURFACES,THE UPPER ONE EXTENDING AFT OF THE SHOULDER TO THE STERN ANDCONSTITUTING A TAIL SURFACE AND THE LOWER ONE EXTENDING FORWARDLY OF THESHOULDER AND CONSTITUTING A PLANING SURFACE, THE PORTION OF THE BOARDAFT OF SAID SHOULDER BEING A SCORPION TAIL WHOSE SIDES TAPER INWARDLYTOWARDS THE STERN TO PROVIDE A CUTAWAY PORTION BETWEEN THE SIDES OF THETAIL AND EXTENSIONS OF THE BOARD AFT OF SAID SHOULDER, AND A SKEGDEPENDING FROM THE AFTER END OF SAID PLANING SURFACE THE NORMAL STANCEOF THE RIDER FOR PLANING BEING WITH ONE FOOT OVER THE SKEG AND THE OTHERFOOT FORWARDLY THEREOF OVER THE PLANING SURFACE.